HEAVY USE OF MARIJUANA CAUSES DROP IN IQ: STUDY

Level Can Recover If Smokers Refrain From Drug For Three Months

Heavy marijuana use decreases IQ by an average of four points, according to
a new study in the Canadian Medical Association Journal.

The good news is that IQ can recover if smokers stay clean for three months
or more, said Dr. Paul Fried, a professor of psychology at Carleton
University in Ottawa and the study's lead author.

"But we have to be very cautious. IQ is a rather insensitive measure and if
we look at things like attention, memory and (information) processing
speed, we don't know if they recover or not."

While the findings are positive news for young recreational marijuana
users, it would be a leap to conclude that 40- and 50-year-olds who have
been smoking dope for decades can count on the same recovery, Fried said.

Heavy use was defined in the study, published today, as smoking more than
five joints per week.

The study involved young middle-class adults with above-average
intelligence who had used marijuana for just three years and did not
regularly use other drugs.

"Whether (IQ) recovery would occur in older folks who may have been using
it for many, many years and may have a riskier lifestyle, we don't know,"
Fried said.

The issue of whether marijuana use has an impact on IQ is contentious.
About 50 studies have been done on the subject and the results are evenly
split.

The Carleton study is unique in that researchers were able to compare
before and after IQ profiles for each participant.

Since 1978, they have been following a group of children whose mothers
enrolled in the Ottawa Prenatal Prospective Study. Those children are now
aged 17 to 20.

Researchers studied a subset of 70 young adults to examine the effects of
marijuana on IQ.

They compared current IQ scores to those on file from the subjects'
pre-marijuana days, between ages 9 and 12.

Before initiation of marijuana use, subjects had a mean IQ score of 109. A
score of 100 is considered average. Special education is typically offered
to those with an IQ of 77 or below.

Nine of the subjects were currently light marijuana users -- defined as
less than five joints per week. Another nine were former pot smokers who
hadn't used the drug for at least three months. Fifteen were heavy users
and 37 were non-users who had never smoked the drug on a regular basis.

Researchers used urine samples to confirm marijuana use or abstinence.

Current heavy users showed a decline in IQ of 4.1 points, which is in the
range of the decrease seen among children whose mothers consumed three
alcoholic drinks a day while pregnant or who used cocaine during their
pregnancy.

"A change of four points for an individual is not something a teacher or
you would notice while walking down the street," Fried said.

The decrease in IQ was not seen in former heavy users.

"This lack of a negative impact among the former heavy users is striking,
as they smoked on average an estimated 5,793 joints over 3.2 years (mean of
37 joints per week). In contrast, the current heavy users had smoked on
average an estimated 2,386 joints over 3.1 years (mean of 14 joints per
week)," the article said.

While there is little evidence that marijuana produces physiological
addiction, there is research to support psychological addiction, Fried said.

"If somebody is using it as their sole crutch for dealing with stress and
anxiety, or they spend a lot of time thinking where the next joint is
coming from, that's a pretty good definition of psychological addiction and
that's not a good thing."

An estimated 1.5 million Canadians use marijuana on a regular basis.